1. Field of the Invention
The invention relates to a slip ring assembly for transmitting electrical signals by means of sliding contacts between mutually rotatable parts. At least one sliding contact, which is also known as a brush and is made of an electrically conductive material, will slide on a slideway which is also made of an electrically conductive material. As a result of the galvanic contact between the slideways and the contact it is possible to transfer electric current.
2. Description of Relevant Art
EP 0 662 736 A discloses a slip ring assembly in which a brush runs with several wires in a V-groove. This leads to a low contact resistance by connecting several contacts in parallel.
A slip ring assembly is disclosed in DE 14 89 080 A in which the brushes in form of massive individual wires run in grooves of a slideway.
U.S. Pat. No. 4,398,113 discloses a further brush with several wires. In this case, the slideway has a lower hardness than the brush, so that soft gold from the slideway will adhere to the brush during initial running of the brush. This leads to a durable and low-friction coating on the brush.
DE 34 34 627 A1 discloses a slip ring assembly in which a hard amorphous intermediate layer is arranged under a conductive contact layer. This amorphous intermediate layer supports the contact layer and ensures that it is provided with a long useful life in combination with low abrasion.
In order to achieve good transmission properties, the pairings of contacts, i.e. the outer metal layers of the brushes and the slideways, are made of electrically well-conducting and abrasion-proof materials. Layers based on gold are preferably used. Wear of brushes and/or slideways still occurs frequently after longer periods of operation. If the gold layer of a slideway is damaged, the brush runs on the layer situated beneath said slideway, which comprises nickel or another similar metal. Massive contact disturbances immediately occur here, leading to strong abrasion of the brush. In such defects, it is frequently only possible to completely exchange the brush and the slideway.